Move webpack config for sass to a separate directory

Sass files will be compiled into CSS files into the same folder (/static/css/) as it was done with libsass and setuptools.
The resulting files in /static/css will have same layout and names as with the previous solution, except for /static/css/foundation folder. It is dropped completely since it was empty when built with setuptools. This is expected since /sass/foundation folder contains only Sass partials.

frontend/webpack.sass.config.js

@@ -0,0 +1,55 @@
+const path = require('path');
+const glob = require('glob');
+
+const MiniCssExtractPlugin = require('mini-css-extract-plugin');
+const RemoveEmptyScriptsPlugin = require('webpack-remove-empty-scripts');
+
+const isProduction = process.env.NODE_ENV === 'production';
+
+const stylesHandler = MiniCssExtractPlugin.loader;
+
+const config = {
+    entry: {
+        nav: path.resolve(__dirname, '../python/nav/web/sass/nav.scss'),
+        ...glob.sync('../python/nav/web/sass/nav/**.scss').filter(v => !path.parse(v).name.startsWith('_')).reduce(function (obj, el) {
+            obj[`nav/${path.parse(el).name}`] = el;
+            return obj
+        }, {}),
+        'font-awesome/font-awesome': path.resolve(__dirname, '../python/nav/web/sass/font-awesome/font-awesome.scss'),
+    },
+    output: {
+        path: path.join(__dirname, '../python/nav/web/static/css'),
+        clean: true,
+    },
+    devServer: {
+        open: true,
+        host: 'localhost',
+    },
+    plugins: [
+        new MiniCssExtractPlugin(),
+        new RemoveEmptyScriptsPlugin(),
+    ],
+    module: {
+        rules: [
+            {
+                test: /\.s[ac]ss$/i,
+                use: [stylesHandler, 'css-loader', 'sass-loader'],
+            },
+            {
+                test: /\.(eot|svg|ttf|woff|woff2|png|jpg|gif)$/i,
+                type: 'asset'
+            },
+        ],
+    },
+};
+
+module.exports = () => {
+    if (isProduction) {
+        config.mode = 'production';
+
+
+    } else {
+        config.mode = 'development';
+    }
+    return config;
+};